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Editorial Team
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Asked: 2026-05-27T01:31:34+00:00

Situation: need to find which layer the user has touched. Problem: Apple says we

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Situation: need to find which layer the user has touched.

Problem: Apple says we should use [CALayer presentationLayer] to do hit-testing, so that it represents what is actually on screen at the time (it captures info mid-animation etc).

…except: presentationLayer does NOT return the original layers, it returns copies of them … so: the hitTest will return a brand new CALayer instance that is not equivalent to the original.

How do we find which actual CALayer was hit?

e.g.

CALayer* x = [CALayer layer];
CALayer* y = [CALayer layer];
[self.view.layer addSublayer: x];
[self.view.layer addSublayer: y];

...

CALayer* touchedLayer = [self.view.layer.presentationLayer hitTest:touchPoint];

…but, is touchedLayer “x”, or is it “y”?

if( touchedLayer == x ) // this won't work, because touchedLayer is - by definition from Apple - a new object
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1 Answer

  1. Editorial Team

    Ah! Just figured this out, reading a mailing list post on a different problem with CALayer.

    After calling [CALayer presentationLayer], and working with the “presentation clone” of the layer-tree, you can take any object in that tree, and call [CALayer modelLayer] on it to get back the original reference object at the same position in the original tree.

    This reference is stable (tested – it works).

    Apple’s docs are a bit … obscure … on this one. And they imply it will “sometimes” fail (“…results are undefined“) – but it’s good enough for me for now.

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